This invention relates to a rupturable sealing structure of a cell which normally prevents electrolyte from leaking therethrough but which allows a gas abnormally developed in the cell to be released therefrom by rupture of a sealing gasket.
It is known to provide a rupturable sealing gasket in a cell. The gasket normally has a thin part which can be expanded outwardly by an abnormal gas pressure developed in the cell and finally ruptured by the increase of the gas pressure. However, it has been very difficult to integrally form or mold the thin part in the gasket such that the thin part can be ruptured without fail when the internal gas pressure is developed upto a certain critical value.
Accordingly, another proposal has been made as shown in U.S. Pat. No. 3,314,824 in which a sharp member is provided in the cell adjacent to a gasket to puncture the latter when the internal gas pressure is abnormally increased in the cell. This proposed structure, however, requires the additional sharp member which causes not only the reduction of the effective internal volume of the cell but also the increase of the production costs of the cell.